1. Field of the Invention
The present invention relates to a sensor and a method for fabricating the sensor; and, more particularly, to a suspended nanowire sensor having good sensing characteristics and suitable for mass production, a method for fabricating the suspended nanowire sensor.
This work was supported by the National Research Laboratory (NRL) program of the Korean Ministry of Science and Technology (MOST)/the Korea Science and Engineering Foundation (KOSEF).
2. Description of Related Art
Much research is being conducted on nanomaterial sensors. Owing to specific characteristics of nanomaterials such as a relatively large surface area compared with a small size, uniform properties, and unique chemical reactive properties, nanomaterial sensors can have better performance than other sensors. For example, it is known that when a chemical sensor is formed of a metal oxide having a uniform and nanoscale particle size, the sensing characteristics of the chemical sensor can be largely improved.
Furthermore, some research articles (Science 287, 622) show that the use of a carbon nanotube (CNT) material for sensors increases the operating temperature range and sensitivity of the sensors and reduces the size of the sensors. In addition, it is also known that the use of other nanomaterials such as semiconductor silicon nanowires and metal oxide nanowires allows an improvement in the characteristics of sensors.
Although many synthesis technologies for nanomaterials such as nanowires or CNTs have been developed, the development of nanomaterial devices such as nanowire sensors and manufacturing technologies for the nanomaterial devices is insufficient.
FIG. 1 is a cross-sectional view illustrating a conventional nanowire sensor. Referring to FIG. 1, the conventional nanowire sensor includes a substrate 11, an insulation layer 12 formed on the substrate 11, a nanowire sensor material layer 14 formed on the insulation layer 12, and sensor electrodes 13 contacting the nanowire sensor material layer 14. The nanowire sensor material layer 14 can be directly formed above the substrate 11. Alternatively, the nanowire sensor material layer 14 can be formed by applying a liquid containing nanowires to the substrate 11.
The conventional nanowire sensor can be classified into two types according to the shape of the nanowire sensor material layer 14. In one type, the nanowire sensor material layer 14 is made up of one or several pieces. In the other type, the nanowire sensor material layer 14 is made up of plural pieces that are formed of a nanowire aggregation and are arbitrarily arranged above the substrate 11.
In the former type, the sensor electrodes 13 are connected to the pieces of the nanowire sensor material layer 14 by aligning the sensor electrodes 13 with the pieces of the nanowire sensor material layer 14 using information about the locations of the pieces of the nanowire sensor material layer 14 obtained using a scanning electron microscope (SEM) or an atomic force microscope (AFM). Therefore, the nanowire sensor of the former type is not suitable for mass production although it has good sensing characteristics.
In the latter type, since the pieces of the nanowire sensor material layer 14 are arbitrarily arranged, although the nanowire sensor is suitable for mass production, the sensing characteristics of the nanowire sensor can deteriorate due to interaction between the arbitrarily arranged pieces of the nanowire sensor material layer 14.
Moreover, since the nanowire sensor material layer 14 is attached to the substrate 11, the sensing characteristics of the nanowire sensor can deteriorate due to interaction between the nanowire sensor material layer 14 and the substrate 11.